Underground sanitary sewer pipe systems are designed to convey raw sewage, waste water, and the like by gravity flow to waste water treatment facilities where the sewage is processed and the waste water is treated for return to the environment. Municipalities' sanitary sewers are generally designed to carry only waste water and not ground or storm water. However, many sanitary sewer systems contain defects such as cracks, holes, and defective joints where lengths of pipe have shifted apart or where sealing material has become ineffective. As a result of these defects, undesired ground and/or storm water may enter the sanitary sewer system. Conversely, raw sewage may leak out of the sewer pipes (e.g., into the surrounding soil).
Typically, water enters a pipe system in one of two ways: infiltration or inflow. Infiltration occurs when ground water enters the sanitary sewer through a leak or other defect in a pipe. Inflow occurs when storm water is directed to the sanitary sewer through connections such as roof downspouts, ground water sump pumps, and driveway drains.
Where leaking sewer pipes allow infiltration of ground water into the sewer pipes, soil particles are typically suspended in the ground water and flow into the sewer pipe, leaving voids in the soil where such suspended soil particles originated. When voids are left on the outside of the pipe, the surrounding soil no longer supports the sewer pipe, which may sag or move. This aggravates the existing defects and creates additional defects.
Once storm and ground water enters the sanitary sewer system, it must be moved and treated in the same manner as sewage thus increasing treatment costs and depleting the hydraulic capacity of the sewer system. Additionally, where excessive amounts of storm or ground water enter the sanitary sewer system, sewage may back up into residents' homes or overflow into waterways creating a health hazard and requiring expensive cleanup measures. Moreover, where defects are left unrepaired, large voids may be created causing potholes, sinkholes, or the total collapse of streets or other constructions located above such sewer pipes.
Alleviation of the adverse effects of infiltration and inflow currently consists of detecting the source of the infiltration and/or inflow by traveling to manholes and residences and visually inspecting the connections or manually sending cameras through the sewers and subsequently repairing the defect(s).
Conventional pipe inspection involves the use a camera, either mounted on a semi-rigid pushrod and pushed into a piping system or transported via a robot crawler. In this manner, an operator is able to visually inspect a pipe for leaks. In either instance, the range of the camera is physically limited by, for example, the length of the pushrod, the length robot's cables, etc. Also, inspection occurs only after someone first identifies a potential problem. For example, if a leak is suspected, one or more flow meters may be positioned in the piping system to detect excessive flow. But if the infiltration or inflow only occurs during periods of high volume (e.g., immediately following a storm), the window for effective inspection may have already passed by the time the flow meters are installed.